Google, researchers create first detailed map of global forest change

The first high-resolution global map of forest resources has been created by a multiorganizational team including University of Maryland, Google and international university and government researchers. The free tool helps scientists understand human and naturally induced forest changes and how these changes affect other natural and societal systems, members of the team say.

To build this first-of-its-kind forest mapping resource, researchers drew on satellite data to measure changes in forest and other types of land cover. Landsat 7 data from 1999 through 2012 were obtained from a free archive at the United States Geological Survey's center for Earth Resources Observation and Science (EROS). More than 650,000 Landsat images were processed to derive the final status of forest change.

The analysis was made possible through a collaboration with Google Earth Engine colleagues who used models developed at the University of Maryland for characterizing the Landsat data sets. Google Earth Engine is a massively parallel technology for high-performance processing of geospatial data and houses a copy of the entire Landsat image catalog. What would have taken a single computer 15 years to perform was completed in a matter of days using Google Earth Engine computing, University of Maryland officials said in a release.

The Google Earth Engine data sets, which span more than 25 years, have been available to researchers for a few years. Google collected, cataloged and stored over 900 terabytes of USGS and NASA Landsat images from as far back as the 1970s and put it in the Google cloud.

In the study using the tool, the team of 15 university, Google and government researchers reported a global loss of 2.3 million square kilometers (888,000 square miles) of forest between 2000 and 2012 and a gain of 800,000 square kilometers (309,000 square miles) of new forest.

"This is the first map of forest change that is globally consistent and locally relevant," says University of Maryland Professor of Geographical Sciences Matthew Hansen, team leader and corresponding author on the team’s study, published online on November 14 in the journal Science.

Hansen and his coauthors say their mapping tool greatly improves upon existing knowledge of global forest cover by providing fine resolution (30 meter) maps that accurately and consistently quantify annual loss or gain of forest over more than a decade. The database, which will be updated annually, quantifies all forest stand-replacement disturbances due to logging, fire, disease or storms.

Hansen and colleagues say the global data sets of forest change they have created contain information that can provide a "transparent, sound and consistent basis to quantify critical environmental issues," including the causes of the mapped changes in the amount of forest.

"Brazil used Landsat data to document its deforestation trends, then used this information in its policy formulation and implementation," Hansen said. "Such data have not been generically available for other parts of the world. Now, with our global mapping of forest changes every nation has access to this kind of information, for their own country and the rest of the world."

About the Author

Susan Miller is the executive editor of GCN. Follow her on Twitter: @sjaymiller.